This happened in the past as well about 6 months ago, and it seems to be back. Was doing FGII vet last night and it was scaled to near trials-difficulty despite using the dungeon finder to get in there and running with competent guildies and a solid healer.
To give an idea how off the scaling was, I use merchants to repair, and a typical vet dungeon is in the $100-500 worth of repairs at most depending on how good the group is and this dungeon had me $1500+ worth of damage armor to repair.
Either it's scaling wrong, bugged, or difficulty set itself to something akin to a 6-8 person group.
Extremely irritating to try to explain this to people that claim it's "normal" s they don't seem to understand the difficulty SCALES wrong.